Calculating instrument

ABSTRACT

A calculating instrument for use by children wherein a dial disk indexes one of two digit wheels and the one wheel indexes the other wheel. The wheels are mounted in a housing behind windows each of which exposes a single digit on the respective wheel. Each digit on the other wheel represents a numerical value 10 times the value of a digit on the one wheel and the wheels drive endless belts respectively having rows of unit symbols and decade symbols. A third digit wheel is indexed in response to successive manipulations of the dial disk when the instrument is set to perform a multiplication or division. The digits of the third wheel represent a series of multiplicands or quotients.

Patented Feb. 29, 1972 8 Sheets-Sheet 1 INVENTOR. r'o

"H ml 4 Writ- Patented Feb. 29, 1972 8 Sheets-Sheet a I uvmvron .21 1 APatented Feb. 29, 1972 8 Sheets-Sheet 5 Fig.3

iii-ll REE I IL INVENTOR. V 2r a 2 $24;

Patented Feb. 29, 1972 8 Sheets-Sheet 4 lnl R m m m Patented Feb. 29,1972 8 Sheets-Sheet 6 INVENTOR.

AHA A Patented Feb. 29, 1972 8 Sheets-Sheet 8 Fig.9 148 as 9' e5 1 ICALCULATING INSTRUMENT BACKGROUND OF THE INVENTION The present inventionrelates to calculating instruments in general, and more particularly toimprovements in calculating instruments which can be utilized bychildren to perform simple arithmetical processes, such as addition,subtraction, multiplication and/or division.

At the present time, the simplest calculating instrument is the abacuswherein l rows of beads are strung on horizontal wires which are mountedin a frame. Such instruments are used by children and by adults. Inlearning the rudiments of arithmetic, the child pushes the beads alongthe respective wire, to the right in order to perform an addition and tothe left in order to perform a subtraction. A drawback of suchinstruments is that the child is not visually apprised of therelationship between the numerical expressions in a problem and thenumber of beads at the leftor right-hand side of the frame. Moreover,the abacus is not a satisfactory instrument to apprise children of theimportance and meaning of decimals. Still further, the result of acalculation with the abacus does not appear in the form of a concretenumber or a set of numbers, i.e., the child must count the number ofbeads at the one and/or the other side of the frame in order to arriveat a desired result, Finally, the result of an arithmetical process isdeterminable only while the frame is held in a position in which thebeads cannot slide along the respective wires so that the entireoperation must begin anew if the instrument is accidentally shaken inthe course of a given operation.

SUMMARY OF THE INVENTION instrument which is particularly suited toapprise children of the meaning and importance of decimal points,especially of the relationship between unit symbols, decade symbolsand/or "hundreds symbols, and which furnishes numerical expressions ofthe results of various arithmetical processes, for example, of the twobasic operations (addition and subtraction) or of all four basicoperations (addition, subtraction,

multiplication and division).

A further object of the invention is to provide a calculating instrumentwhich can furnish numerical expressions of ultimate results of basicarithmetical processes as well as intermediate results of suchprocesses, and which enables the user to follow the operation not onlyin the terms of numbers but also in the terms of unit symbols, decade"symbols and, if necessary, hundreds symbols.

An additional object of the invention is to provide a calculatinginstrument whose construction is simple so that it can be understood bya child of average intelligence whereby the child can readily learn themeaning of basic mechanical movements including those performed by dialdisks, wheels, levers, pawls, links, knobs, endless bands or the like.

Still another object of the invention is to provide an instrument whichis constructed and assembled in such a way that its manipulation isinteresting to the user so that a child is not bored while performingvarious calculations and that the child is or need not be fully aware ofthe educational value of the instrument.

An ancillary object of the invention is to provide an instrument whichenables the user to record the result of a mentally performedcalculation and to thereupon compare such recorded result with theresult furnished by the instrument.

Still another object of the invention is to provide an instrument whichis not only educational and entertaining but is further designed in away to present a challenge to an interested child, for example, bypermitting recordal of a mentally performed calculation and forconcealment of numerical expressions furnished by the instrument priorto completion of a mechanical calculation.

An additional object of the invention is to provide a calculatinginstrument which enables the user to understand the meaning of signswhich denote the basic arithmetical operations and which is compact andsimple enough to be readily transported between home and school and tobe capable of mass-production at a reasonable cost.

A further object of the invention is to provide a calculating instrumentwhich enables the user to follow the progress of an arithmeticalprocess, not only with the eyes but also with the ears, to thus enablethe user to learn how to concentrate during calculation and to even morereadily comprehend the meaning of addition, subtraction, multiplicationand/or divisron.

The invention is embodied in a calculating instrument, particularly foruse by children, which in its simplest form enables the user to performadditions and subtractions. The instrument comprises carrier meansincluding at least one wheelshaped or belt-shaped carrier provided witha sequence of symbols (in the form of digits or unit or multiple-unitsymbols) and being movable between a plurality of positions in each ofwhich at least one of its symbols assumes a predetermined position torepresent a numerical expression which can be readily seen through awindow or aperture of the housing, and moving means (such as a dialdisk, a finger flange, a reciprocable slide or a pivotable lever) formoving the carrier through a desired number of unit increments each ofwhich corresponds to placing of at least one different symbol into thepredetermined position.

In accordance with a presently preferred embodiment, the housing of theinstrument accommodates at least two coaxial digit wheels each of whichcarries a row of symbols in the form of digits including two sets ofdigits 0 to 9. The moving means preferably comprises a dial disk whichis rotatable in two directions and indexes or increments one of thedigit wheels. The other digit wheel is indexed by the one digit wheelwhen the latter is indexed through a predetermined angle, namely,through an angle which is 10 times a unit angle necessary to move agiven digit on the one wheel away from and to place the next-followingdigit into registry with the corresponding window.

The improved instrument can be designed to perform additions,subtractions, multiplications and divisions. It is then provided with athird digit wheel whose digits represent a series of multiplicands orquotients. The third digit wheel can be indexed by the dial disk.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved calculating instrument itself, however, both as to itsconstruction and its mode of operation, together with additionalfeatures and advantages thereof, will be best understood upon perusal ofthe following detailed description of certain specific embodiments withreference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic plan view of acalculating instrument which embodies one form of my invention and isdesigned to perform additions and subtractions;

FIG. 2 is a sectional view as seen in the direction of arrows from theline II-II of FIG. I;

FIG. 3 is a plan view of the interior of the housing in the calculatinginstrument of FIG. 1, with certain parts omitted and with certain partsshown in section;

FIG. 4 is a transverse sectional view substantially as seen in thedirection of arrows from the line IVIV of FIG. 1;

FIG. 5 is a fragmentary sectional view as seen in the direction ofarrows from the line V-V of FIG. 4;

FIG. 6 is a schematic plan view of a portion of a second calculatinginstrument which is provided with record receiving means enabling theuser to jot down mentally or mechanically determined results ofarithmetical processes;

FIG. 7 illustrates the structure of FIG. 6 and the dial disk, withcertain parts shown in different positions;

FIG. 8 is a schematic plan view of parts in the housing of a thirdcalculating instrument which can perform four different arithmeticalprocesses;

FIG. 9 is a plan view of the instrument shown in FIG. 8; and

FIG. 10 is a transverse sectional view as seen in the direction ofarrows from the line X-X of FIG. 9.

I DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIGS. 1 to5, there is shown a calculating instrument having a main support orhousing 1 which need not be closed from below (see FIG. 2) and whose topwall or panel la supports a rotary dial disk 3 having fnger holes 2. Thewall In is further formed with two elongated apertures 4, 5 torespectively permit observation of unit symbols and decade symbols, andwith two relatively small windows 6, 7 which permit observation ofsymbols in the form of digits provided on two symbol carriers here shownas digit wheels 19, 39 mounted in the interior of the housing 1. Thewall la is further formed with a short arcuate slot 8 for the indexorpointer of a motion transmitting lever 9 which can be moved between twoend positions to respectively register with an addition or plus sign anda subtraction or minus sign. A longer second arcuate slot 10b isadjacent to the periphery of the dial disk 3 and accommodates a portionof an outwardly extending stop 10 which overlies the dial disk 3 and ismovable by finger pressure from the solid-line neutral position to twoend positions which are-shown by broken lines and are denoted bynumerals 11 and 12. A spring 10a is connected to the housing 1 and tothe stop 10 to urge the latter to the solid-line neutral position. Suchmounting of the stop 10 renders it possible to avoid the representationof a zero position.

The dial disk 3 can be rotated in a clockwise direction (arrow 13) or ina counterclockwise direction (arrow 14); it is rotated in a clockwisedirection when the index of the lever 9 registers with the plus sign andin a counterclockwise direction when the index registers with the minussign. The plus and minus signs are shown as being applied directly tothe outer side of the wall la. The lever 9 is connected with a numberwheel 15 (see FIG. 4) which is located below the wall In and has twosets of equidistant numbers, namely, the counterclockwise appliednumbers I to 10 observable in FIG. 1 through the finger holes 2, and theclockwise applied numbers "1 to 10 indicated on the number wheel 15" ofFIG. 9 by dots. The numbers of the two sets alternate with each otherand the angular displacement of the wheel 15 in response to movement ofthe index on the lever 9 from registry with the plus sign into registrywith the minus sign on the wall la suffices to move the set of dottednumbers into registry with the finger holes 2. The other set of numbersis then concealed behind the wall la which is provided with holes eachregistering with one of the finger holes 2. That position of the lever 9in which its index registers with the minus sign on the wall 10 isindicated in FIG. 1 by broken lines, as at 16. When the lever 9 assumesthe position 16 of FIG. 1-, the solidlinenumber 1 directly to the rightof the stop 10 (solid-line position) is replaced by the dotted number10"; the number 2 of FIG. 1 is replaced by the dotted number 9; thenumber 3" of FIG. 1 by the dotted number 8", and so forth. If the dialdisk 3 is then rotated in a counterclockwise direction (arrow 14), a

is inserted into one of the finger holes 2 and the disk is then the endposition 11. When the finger is removed from the finger hole 2, the stopIt) automatically returns to its neutral position under the action ofthe spring 10a but the dial disk 3 remains in the newly selectedposition. The distance between the neutral position and the end position11 or 12 of the stop 10 corresponds to the distance between twosuccessive numbers of either set of numbers on the number wheel 15.

FIG. 4 shows that the dial disk 3 is coaxial with and secured to a firstbevel gear 17 which forms part of a transmission further including asecond bevel gear 18 which indexes the first digit wheel 19. The latteris accommodated in the interior of the housing 1 and its axis ispreferably normal to the axis of the dial disk 3. The wheel 19 isprovided with a finger flange 20 having 20 lugs or teeth and with acylindrical hub 204 which is adjacent to the finger flange 20 and isprovided with two groups of digits 0" to 9 which form a single row inline with the window 6. The hub 20a can be omitted if the two groups ofdigits are provided on an endless symbol carrier belt or tape 23 whichis trainedover and driven by the digit wheel 19. The means for drivingthe belt 23 comprises a sprocket 21 whose teeth can enter perforations22 (see FIG. 2) of the belt 23. The latter is further trained over apulley 24 which is rotatable in the housing 1.

The calculating instrument is provided with a yieldable detent devicefor the digit wheel 19. This detent device is shown in FIG. 2 andcomprises a roll or ball 26 which is biased by a spring 25 reactingagainst the housing 1 so that the roll 26 engages the finger flange 20.When the flange 20 is rotated by hand (see FIG. 2 which shows thatseveral lugs of the flange 20 are accessible at the outer side of thewall 1a), the roll 26 ratchets over the lugs of the flange 20 andpreferably produces a series of sounds which can be counted to thusenable the user to totalize the number of clicks" and to follow thearithmetical process with his or her ears.

The second digit wheel 39 is coaxial with the digit wheel 19 and isprovided with a finger flange 41 several lugs of which are accessible atthe outer side of the wall In. A second springbiased detent roll (notshown) cooperates with the lugs of the finger flange 41 to producecharacteristic sounds when the digit wheel 39 is rotated. This latterwheel comprises a cylindrical rim or hub 40 provided with two sets ofsymbols or digits 0 to 9 which form a single row, and a sprocket 42whose teeth can enter perforations 43 provided in a second endlesssymbol carrier belt or tape 44 which is trained over the digit wheel 39and over a pulley 45 in the housing 1. The bias of springs which formpart of the detent means is preferably weak so that a child can turn thedigit wheel 19 or 39 with a minimum of effort. The finger flanges 20, 41constitute an optional feature of the calculating instrument because thedigit wheels 19, 39 can be indexed by the dial disk 3. An advantage ofsuch finger flanges is that the user can place a digit 0" into registrywith the window 6 and/or 7. The feature that the digit wheels 19, 39 areindexible by the dial disk 3 as well as independently of such dial diskenhances the versatility of the calculating instrument.

As shown in FIG. 1, the endless belt 23 is provided with two parallelrows 27, 28 of unit symbols. The two rows are offset with reference toeach other as considered in the circumferential direction of the belt23. The right-hand portion of the aperture 4 is obscured by an opaquemask 29 and the lefthand portion of this aperture exposes in FIG. I aportion of the row 27, namely, four unit symbols. Such symbols may butneed not be encircled. The mask 29 overlies five unit symbols of the row28, such obscured unit symbols being indicated by broken lines. Themanner in which the mask 29 can be shifted with reference to theaperture 4 of the wall la will be explained below. Shifting of the mask29 takes place automatically when the aperture 4 exposes nine unitsymbols of the row 27 or 28. Each of the windows 6, 7 exposes a singledigit on the hub 20a, 40 respectively.

FIG. 4 illustrates that the body of the digit wheel 19 supports tworadially movable entraining or indexing posts or pins 30, 31. These pinsare installed in radially extending slots 30a of the digit wheel 19 andare biased outwardly by helical springs 32, 33. The pins 34), 31 arelocated diametrically opposite each other and constitute two followerswhich can track the face of a stationary cam 334 mounted in thehousing 1. When the digit wheel 19 rotates, the pin 30 or 31 travelsalong the cam 334 and is caused to move radially inwardly intoengagement with the teeth of an indexible motion receiving gear 38 onthe second digit wheel 39. The configuration of the face on the cam 334is shown in FIG. 5; this face comprises two inclined sections 34, 37flanking a top land or median section 336. When the digit wheel 19rotates in a clockwise direction, as viewed in FIG. 5, its pin 30travels along the section 34 and is caused to move radially inwardly(i.e., toward the axis of the wheel 19) whereby its exposed end portionenters the space between the adjoining teeth of the gear 38 to index thedigit wheel 39 in a clockwise direction and through an angle ofpredetermined magnitude. Once the pin 30 moves beyond the top land 336,it travels along the section 37 (under the bias of the spring 32) and isdisengaged from the gear 38 so that the digit wheel 39 then remains inits new angular position. When the digit wheel 19 is caused to rotate ina counterclockwise direction, as viewed in FIG. 5, the pin 30 or 31moves along the section 37, thereupon along the top land 336, andfinally along the section 34 to thus increment the digit wheel 39 in acounterclockwise direction. The digit wheel 39 is incremented wheneverthe hub 20:: of the digit wheel 19 moves a digit 9" beyond the window 6,i.e., whenever this window exposes a (while the dial disk 3 is rotatedin a clockwise direction as indicated by the arrow 13 of FIG. 1). Whenthe dial disk 3 is rotated in the direction indicated by arrow 14(subtraction), the digit wheel 39 is incremented whenever a digit on thehub 20a disappears, i.e., whenever the window 6 begins to expose a digit9. The pin 30 or 31 then travels from the section 37 toward the section34 of the face on the cam 334.

The belt 441 which is associated with the digit wheel 39 is providedwith a single row 46 of decade symbols which can be observed in theaperture 5. It is clear, however, that the belt 44 carries two rows ofdecade symbols if the calculating instrument is designed to carry outarithmetical processes which involve addition of numbers to form a sumin excess of 100. The instrument then comprises a third digit wheel (notshown) which is incremented by the digit wheel 39 in the same way asdescribed in connection with indexing of the wheel 39 and which thendrives a third symbol carrier tape or belt having a row of hundredsymbols. The instrument then also comprises a second mask for theaperture and the wall 1a is then provided with an additional aperturecorresponding to the aperture 5 and registering with the row of hundredsymbols on the third belt.

The distribution of symbols in the rows 27, 28 and 46 on the belts 29,44 is such that the number of unit symbols which are observable in theaperture 4 is indicated by the digit which is observable in the window6, and that the number of decade symbols which are observable in theaperture 5 is indicated by the digit which can be seen in the window 7.In the setting of digit wheels 19, 39 as shown in FIG. 1, the aperture 4exposes four unit symbols of the row 27 because the user can see a digit4 on the hub a of the wheel 19. The aperture 5 exposes three decadesymbols because a digit 3 on the hub 40 of the wheel 39 is observable inthe window 7. It is immaterial whether the digit wheel 19 is rotated inresponse to rotation of the dial disk 3 or in response to rotation ofthe finger flange 20.

In accordance with a slight modification which is not shown in thedrawing, the calculating instrument of FIGS. 1 to 5 can be provided witha second mask which automatically conceals or exposes a single-decadesymbol behind the window 5 when the mask 29 is caused to change itsposition. The digit wheel 39 is then omitted, together with the pulley45 and belt 44, but the aperture 4 must be enlarged and the number ofunit symbols on the belt 23 must be augmented in such a way that 10 unitsymbols can simultaneously appear behind the thus enlarged aperture 4.

The manner in which the mask 29 is shiftable with reference to the wall1a of the housing 1 is illustrated in FIG. 3. The mask 29 is locateddirectly behind the front wall in and is formed with an elongatedopening or slit 48 whose size equals or approximates half the size ofthe aperture 4. In the solidline position of FIG. 3, the opening 48registers with the lefthand portion of the aperture 4 and permitsobservation of selected unit symbols in the row 27. When moved to thebroken line position 439, the opening 48 registers with the right-handportion of the aperture 4 and exposes a seiected number of unit symbolsin the row 28. The mask 29 has a lug 29a provided with a pin 59 whichextends into m open slot 51a defined by a bifurcated end portion or claw51 of a shifting lever 52. The other end portion of the lever 52 isturn-able on a fixed pivot 53 and its median portion is formed with acutout 54 for a fixed shaft 55. A helical spring 56 is coupled to thelever 52 and tends to turn it in a clockwise direction, as viewed inFIG. 3, so that the mask 29 tends to assume its lefthand end positionand to maintain its opening 4% in registry with the left-hand portion ofthe aperture 4. The right-hand end portion of the digit wheel 19 forms aface cam which is provided with axially offset cam face sections 58, 59and two inclined sections 60. A follower 57 of the lever 52 is biasedagainst the face cam by the spring 56 whereby the mask 29 dwells in thesolid-line position of FIG. 3 when the follower 57 engages the section58 but the mask 29 moves to the other end position (indicated by brokenlines) when the follower 57 tracks a section 60 and thereupon engagesthe section 5'9. The spring 56 automatically returns the lever 52 fromthe broken line position 61 to the solid-line position of FIG. 3 whenthe digit wheel 19 is rotated to such an extent that the follower 57 ofthe lever 52 is adjacent to the section 58. The length of each of thecam sections 58, 59 corresponds to the length of a group of digits 0 to9 on the hub 20a of the digit wheel 19. The mask 29 is shifted wheneverthe opening 48 exposes nine unit symbols of the row 27 or 23; suchshifting takes place while a single-unit symbol appears behind theopening 418 as soon as the latter changes its position by moving inaxial direction of the digit wheel 19. If desired, the instrument can beprovided with a device which produces a readily detectable audiblesignal when the mask 29 is caused to change its position; this istantamount to indicating that the sum of numbers represented by the unitsymbols and decade symbols has been changed by ten. One of two acousticsignal generating devices which can be utilized in the calculatinginstrument of FIGS. 1 to 5 is indicated schematically in FIG. 3, as at35%; this device produces an audible signal when the lever 52 moves tothe broken line position 61. The provision of such signal generatingdevices constitutes an optional feature of my invention because at leastsome audibly detectable signals can be produced by the finger flanges20, 41 in cooperation with the respective detent devices.

The parts 19, 39, 23, 44 together constitute a carrier assembly whichcan move selected symbols to predetermined positions in which suchsymbols can be observed through apertures 4, 5 and windows 6, 7 andrepresent given numerical expressions. The parts 3, 17, 18, 30, 31, 38,20 and 41 together constitute a moving assembly which can effect.movements of the carrier assembly to any one of a large number ofdifferent positions.

Referring to FIGS. 6 and '7, there is shown a portion of a modifiedcalculating instrument which is provided with means for facilitating acomparison between the mentally determined and recorded sum or resultand the result which is indicated by the instrument. A sidewall 10111 ofthe housing 191 is provided with a slot for a portion of a two-armeddigit concealing lever or shutter 62 fulcrumed at 63 and having an arm63a which can be moved into registry with the windows 106 and 107. Thefinger flanges 20a, 40 are omitted (see the digit wheels 119, 139 ofFIG. 7) to enable the arm 63a to move into and away from registry withthe windows 106, 107. It is clear, however, that the housing 101 can bedesigned in such a way that the wheels 119, 139 may be replaced bywheels 19, 39 if portions of finger flanges on such wheels extendthrough slots provided, for example, in the end wall 101s of the housing101.

The right-hand arm of the lever 62 is articulately connected with atransparent shield 65 by means of a link 64. The marginal portions ofthe shield 65 are guided by suitable rails or 'ways provided on the wall101a. When the arm 63a registers with the windows 106 and 107, theshield 65 is moved away "from registry with a record receiving orwriting pad 66 (or at least with a line of such pad) so that the usercan write down the arithmetical operation which is to be performed orwhich has just been completed. The result of calculation written down onthe pad 66 can be compared with the result which is observable in thewindows 106, 107 when the lever 62 is thereupon pivoted to the positionshown in FIG. 7. The shield 65 then overlies the pad 66 but its arm 63apermits observation of digits 3" and 4 behind the windows 107, 106,respectively. In performing the operation which is written down on thepad 66, the user of the instrument can refer to decade symbols and unitsymbols which are observable in the apertures 105 and 104 of the wall101a. The pad 66 can be replaced with a roll of writing paper mounted inthe housing 101 behind a suitable window in the wall 101a so that aline, ready for writing down a series of numerical expressions, isaccessible as soon as the lever 62 is moved to the position of FIG. 6.The roll of paper can be advanced automatically in response to movementof the lever 62 from the position of FIG. 7 to the position of FIG. 6(i.e., counter to the direction indicated by arrow B of FIG. 7).

If desired, the pad 66 can constitute a writing tablet which can bereadily wiped clean, either by the user or automatically in response tomovement of the shield 65 from the position of FIG. 7 to the position ofFIG. 6.

The manner in which the dial disk 3 (shown in FIG. 7) is mounted andcoupled to the digit wheel 119 is the same as described for the disk 3and wheel 19 of FIG. 1.

Referring finally to FIGS. 8 to 10, there is shown a third calculatinginstrument wherein the dial disk 3 and the .digit wheels 19, 39 aremounted and operated in the same way as described in connection withFIG. 1. In FIG. 8, the front wall 201a of the housing 201 is omitted andthe dial disk 3 is indicated by phantom lines. The instrument of FIGS. 8to can perform four different operations, namely, addition, subtraction,multiplication and division. Addition and subtraction are performed inthe same way as described in connection with FIGS. 1 to 5.

The stop 210 is mounted on a lever 67 which forms part of a linkage andis tumable about the axis of the dial disk 3. The lever 67 isarticulately connected to a link 68 which latter is pivotally connectedto a median portion of a further lever 69. One end of the lever 69 istumable on a pivot 70 in the housing 201 and its other end carries apivotable pawl 71 having a bentover pallet or arm 72 which normallyengages an abutment 73. The other arm 74 of the pawl 71 is coupled to aspring 75 which urges the pallet 72 against the abutment 73. The spring75 is connected to the lever 69. When the dial disk 3 is rotated and theusers finger moves the stop 210 to the end position 211 or 212, thelever 67 pivots the lever 69 by way of the link 68. The lever 69 turnsin a clockwise direction so that the pallet 72 moves beyond the abutment73. The spring 75 then contracts and moves the pallet 72 against theteeth 76 of a further digit wheel 77 which is rotatable in the housing201 and has a finger flange 77a some lugs of which extend through a slotin the wall 201a. The angular movement of the lever 69 is terminatedwhen the pallet 72 increments the digit wheel 77 through a predeterminedangle. The hub 77b of the digit wheel 77 carries two groups of digits lto 9 which form a single row. One digit is observable behind a window 70of the front wall 201a. With reference to FIG. 0, the pallet 72 movesdownwardly when the stop 210 is moved to the end position 211 or 212.Thus, the lever 69 is always pivoted in the same direction (clockwise,as viewed in MG. 0) irrespective of whether the stop 210 moves to theposition 211 or 212. Each movement of the stop 210 to the position 211or 212 results in such angular displacement of the digit wheel 77 thatthe hub 77b moves the next-following digit into registry with the window78.

The manner in which the instrument is to be set prior to carrying out amultiplication or division is illustrated in H6. 9. The purpose of suchsetting is to enable the user to readily understand the operation whichis being performed and to be able to identify such operations byobservation of appropriate signs. Indexing of the digit wheel 77 is oneindication that the instrument is in the process of carrying out eithera multiplication or a division.

For example, if a child is to execute a simple multiplication (5X2), thefinger is repeatedly inserted into the finger hole 2 above the number 2,and the dial disk 3 is turned five times in a clockwise direction (arrow13) to move the stop 210 to the end position 212. The product (10) isobservable in the windows 207, 206. The digit behind the window 70indicates the number of successive incrementations of the digit wheel77. The digits behind the windows 207, 206 further indicate theintermediate product (e.g., the window 207 will expose the digit 0, thewindow 206 will expose the digit 8, and the window 70 will expose thedigit 4 upon completion of four rotations of the dial disk 3, it beingassumed that the wheels 19, 39 and 77 were reset to zero prior to startof the multiplication). Thus, the child can observe the increase of theproduct from zero to 10, which is a simple and effective way ofcomprehending the meaning of multiplicand, multiplicator and product.

A division is performed in an analogous way. For example, if the childis to divide 10 by 2, the digit wheels 39, 19 are set in such a way thatthe windows 207, 206 respectively expose a digit l and a digit 0. Thedigit wheel 77 is reset to zero (by rotating the finger flange 77a). Thelever 9 is moved to the position 16 so that the finger holes 2 registerwith the dotted numbers of the number wheel 15' and the finger isinserted into the finger hole 2 above the dotted number 2." The disk 3is thereupon rotated in a counterclockwise direction (arrow 14) to movethe stop 210 to the end position 211. This is repeated four times, i.e.,until each of the windows 207, 206 exposes a digit 0. The quotient (5)can be seen behind the window 78. The child is thereby apprised of thefact that the division corresponds to repeated subtraction of a divisorfrom the dividend, and the child also learns that certain dividendscannot be divided with a divisor without a rest. The digit which isobservable behind the window 78 apprises the child of the number ofsubtractions of the divisor (2) from the dividend (10). It will be seenthat, while a product must be read behind the windows 207 206, aquotient can be seen behind the window 78.

The instrument of FIGS. 8 to 10 is further provided with arresting orblocking means which prevents rotation of the digit wheel 77 when theuser performs an addition or subtraction.

Such arresting means comprises a blocking lever 79 which is tumable on afixed pivot 00 of the housing 201. The free end of the lever 79 isprovided with a projection or tongue 81 which can be moved to thephantomline position of MG. 0 to thereby engage the arm 74 of the pawl71 on the lever 69. The pawl 71 is then held in a position in which itspallet 72 cannot index the digit wheel 77 when the stop 210 is moved tothe end position 211 or 212. The means for pivoting the lever 79 betweenthe solid-line and phantom-line positions of FIG. 8 comprises a modifiedmotion transmitting lever 9' which is pivotably mounted in the housing201 (pivot 290 in FIG. 10) and extends through a slot 02 of the lever79. The lever 9' further extends through a slot 83 of the wall 201a andis movable by hand to perform its basic function of turning the dialdisk 15. The slot 83 is wider than the slot 8 of FIG. 1; this enablesthe lever 9' to move to one of four different positions to berespectively adjacent to a plus sign, a minus sign, a multiplicationsign (x) and a division sign (z), When the accessible portion of thelever 9 is adjacent to the plus sign or to the minus sign, the tongue 81of the arresting lever 79 blocks the pawl 71 and prevents indexing ofthe digit wheel 77 in response to movement of the stop 210 to theposition 211 or 212. The tongue 81 is automatically disengaged from thearm 74 of the pawl 71 when the exposed portion of the lever 9 is movedinto alignment with the division or multiplication sign. The pawl 71 isthen free to index the digit wheel 77 in response to angulardisplacement of the stop 210 in either direction.

The number wheel 15' is formed with a bifurcated extension 84. having aradially extending slot 85 for the lever 9'. Thus, the wheel 15 isturned in automatic response to movement of the lever 9' in thedirection indicated by arrow 13 or 14. The slot 85 permits the lever 9'to move from the plus sign to the multiplication sign or vice versa orto move from the minus sign to the division sign or vice versa. Asstated before, the lever 79 maintains its tongue 81 in engagement withthe arm 74 of the pawl 71 when the lever 9' is moved from the plus signto the minus sign or vice versa; however, the lever 79 releases the pawl71 when the lever 9' is moved from the plus sign to the multiplicationsign, from the minus sign to the division sign, from the division signto the multiplication sign, or from the multiplication sign to thedivision sign.

The shaft 203 of the dial disk 3 in the instrument of FIGS. 8 to 10carries a transparent or translucent circular plate 86 provided with apointer 87 which registers with the number 2 on the number wheel Theplate 86 serves as a memory aid in that its pointer 87 indicates thedivisor or multiplicator while the user performs a division ormultiplication. The plate 86 has an upstanding lug 86a and the shaft 203has a set of equidistant notches or flutes 88, one for each of the 10numbers which are observable through the finger holes 2. An elastic pawl89 of the plate 86 enters the adjoining notch 88 when the pointer 87 ismoved into registry with a selected finger hole 2. The notched portionof the shaft 203 constitutes a simple ratchet which cooperates with thepawl 89 to yieldably hold the plate 86 in selected angular position. Oneof the notches 88 is so positioned that the pointer 87 can be moved tothe position 87' of FIG. 9 in which its tip registers with the tip ofthe stop 210 in the neutral position of the stop.

The plate 86 can be replaced with a suitable mask which is thenadjustably fixed to the stop 210 in such a way that it always exposesonly one of the finger holes 2. Such mask can also be mounted on thefront wall 2010.

A writing pad or notebook 90 is provided on the front wall 201a topermit recordal of several arithmetical operations. The pad 90preferably comprises a stack of readily separable sheets. lt is furtherclear that this pad can be replaced with a tablet which is preferablyruled and can be readily wiped clean.

A further shield or mask 92 is mounted behind the front wall 201a andcan be shifted by a knob 91 so as to conceal or expose the digits behindthe windows 2117, 206. The purpose of this mask is analogous to that ofthe shutter lever 62 shown in FIGS. 6 and 7, i.e., a child can conceal asum, quotient or product while attempting to perform a mentalcalculation. The mentally determined result is then written down on thepad 911 or simply memorized before the mask 92 is moved to the positionof FIG. 9 to expose the digits behind the windows 207 and 2116.

If desired, the dial disk 3 can be replaced with a lever which ispivotable with reference to the housing or with a slide which isreciprocable with reference to the housing. The moving assembly thencomprises a suitable mechanism for converting pivotal or reciprocatorymovements into rotary movements of the digit wheels.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featureswhich fairly constitute essential characteristics of the generic andspecific aspects of my contribution to the art.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended 1. In a calculating instrument, particularlyfor use by chil dren, a combination, comprising carrier means comprisingtwo carriers each provided with a sequence of symbols and each includinga rotary digit wheel, said digit wheels being coaxial with each otherand one thereof having indexing means for rotating the other thereofthrough a single increment in response to rotation of said one wheelthrough a predetermined number of increments, the symbols of said wheelsconstituting digits and each of said wheels having a single row ofcircumferentially extending digits including two groups of digits 0 to9"; moving means for moving said carriers through a desired number ofunit increments in each of which at least one difierent symbol islocated in a predetermined position to represent a given numericalexpression, said moving means including a finger flange on each of saidwheels; and yieldable detent means cooperating with said finger flangesto normally hold said means against rotation.

2. In a calculating instrument, particularly for use by children, acombination comprising carrier means comprising a plurality of indexiblewheels including a first and a second wheel each provided with asequence of symbols including a row of digits extendingcircumferentially of each wheel; and moving means for moving said wheelsthrough a desired number of unit increments in each of which at leastone different symbol is located in a predetermined position to representa given numerical value, said moving means comprising a first device forindexing said first wheel through increments of predetermined magnitudeand a second device for indexing said second wheel through a singleincrement in response to indexing of said first wheel through apredetermined number of increments, said second device comprising astationary cam, follower means movably mounted on said first wheel, andmotion receiving means provided on said second wheel, said cam beingarranged to move said follower means into torque transmitting engagementwith said motion receiving means in predetermined angular positions ofsaid first wheel. I

3. In a calculating instrument, particularly for use by children, acombination comprising carrier means including at least one carrierprovided with a sequence of symbols and being movable between aplurality of positions in each of which at least one of said symbolsassumes a predetermined position to represent a given numericalexpression; moving means comprising a rotary dial disk for moving saidcarrier through a desired number of unit increments in each of which atleast one different symbol is located in said predetermined position; anumber wheel registering with said dial disk; and adjustable indicatingmeans for pinpointing a selected number on said wheel.

4. In a calculating instrument, particularly for use by children, acombination, comprising carrier means including at least one carrierprovided with a sequence of symbols and being movable between aplurality of positions in each of which at least one of said symbolsassumes a predetermined position to represent a given numericalexpression; moving means for moving said carrier through a desirednumber of unit increments in each of which at least one different symbolis located in said predetermined position; said moving means comprisinga dial disk which is rotatable in two directions and has a group offinger holes; a support for said dial disk; and a number wheel mountedon said support for movement between two positions, said number wheelhaving a first set of numbers each registering with one of said fingerholes in one position of said number wheel and a second set of numberseach registering with one of said finger holes in the other position ofsaid number wheel.

5. A combination as defined in claim 4, wherein said carrier comprisesan indexible digit wheel.

6. A combination as defined in claim 4, wherein each symbol of saidcarrier represents the same numerical value.

7. A combination as defined in claim 4, wherein the symbols of saidcarrier constitute digits each representing a different numericalexpression.

8. A combination as defined in claim 4, wherein the first of saidcarriers has symbols representing unit values and the second carrier hassymbols representing multiple unit values.

9. A combination as defined in claim 8, wherein each symbol of saidsecond carrier represents 10 unit values.

10. A combination as defined in claim 4, wherein said first set ofnumbers includes a ring of numbers 1-10 running in a clockwise directionand said second set includes a ring of numbers 1-10 running in acounterclockwise direction, the numbers of said first set alternatingwith the numbers of said second set.

11. A combination as defined in claim 4, further comprising stop meansadjacent to said dial disk to arrest the disk by extending into the pathof movement of a finger which is inserted into a selected finger hole torotate said dial disk in one of said directions.

12. A combination as defined in claim 11, wherein said stop normallyassumes a neutral position and is yieldable to finger pressure to movethrough a predetermined distance to either side from said neutralposition.

13. A'combination as defined in claim 12, wherein the numbers of saidsets on said number wheel are equidistant from each other and whereinthe distance between successive numbers of either set corresponds to theextent to which the stop is movable from said neutral position.

14. A combination as defined in claim 4, wherein said carrier comprisesa rotary digit wheel and further comprising yieldable detent means fornormally holding said wheel against rotation.

15. A combination as defined in claim 4, wherein said carrier meanscomprises two carriers each of which constitutes a rotary digit wheelhaving an annulus of symbols including two sets of digits to 9.

16. A combination as defined in claim 4, further comprising means forproducing audible signals in response to each incrementing of saidcarrier.

17. In a calculating instrument, particularly for use by children, acombination comprising carrier means comprising two first carriers eachconstituting an indexible digit wheel and two second carriersconstituting endless belts each'driven by one of said wheels, each ofsaid carriers being provided with a sequence of symbols including a rowof digits provided on and extending circumferentially of each of saidwheels and at least one row of symbols on each of said belts, one row ofsymbols including unit symbols and the other row including decadesymbols; and moving means for moving said carriers through a desirednumber of unit increments in each of which at least one different symbolis located in a predetermined position to represent a give numericalvalue, said moving means including meansfor indexing one of said wheelsthrough increments of predetermined magnitude and means for indexing theother wheel through one increment in response to indexing of said onewheel through 10 increments.

18. A combination as defined in claim 17, further comprising a pair ofpulleys, each of said belts being trained over one of said pulleys andthe respective digit wheel.

19. A combination as defined in claim 18, wherein each of said belts isprovided with a line of perforations and each of respectiveperforations.

20. A combination as defined in claim 17, further comprising a walloverlying said digit wheels and having a pair of winsaid digit wheelscomprises a sprocket whose teeth engage the said belts is provided withtwo rows of unit symbols and wherein one row of said unit symbols isofi'set with reference to the other row of unit symbols.

22. A combination as defined in claim 21, further compris ing maskingmeans movable between first and second positions in which itrespectively conceals the one and the other row of said unit symbols,and means for moving said masking means between said positions inresponse to indexing of the corresponding digit wheel through saidpredetermined number of increments.

23. A combination as defined in claim 22, wherein the means for movingsaid masking means comprises cam means provided on said last-mentioneddigit wheel and shifting means coupled to said masking means and havingfollower means arranged to track said cam means.

24. A combination as defined in claim 17, further comprising a walloverlying said carriers and having a pair of apertures each permittingobservation of a limited number of symbols on one of said belts and apair of windows each pennitting observation of a single digit on one ofsaid wheels.

25. A combination as defined in claim 24, further comprising shuttermeans movable to and from a predetermined position in which it concealsthe digits behind said windows.

26. A combination as defined in claim 25, further comprising recordreceiving means to permit recordal of mentally performed calculationsand shield means operatively connected with said shutter means tooverlie said record receiving means in response to movement of theshutter means away from said predetermined position.

27. A combination as defined in claim 26, wherein said shield meansconsists at least in part of light transmitting material.

28. In a calculating instrument, particularly for use by children, acombination comprising carrier means comprising a pair of firstindexible carriers each provided with a sequence of symbols whichinclude digits, said carriers being movable between a plurality ofpositions in each of which at least one of said symbols assumes apredetermined position to represent a given numerical expression; afirst indexing device actuable to index one of said first carriersthrough increments of unit length; a second indexing device for indexingthe other first carrier by a single increment in response to indexing ofsaid one first carrier through a predetermined number of increments; anadditional indexible carrier having digits representing a series ofnumerical values; and a third indexing device operative to index saidadditional carrier in response to each actuation of said first indexingdevice.

29. A combination as defined in claim 28, wherein the digits of saidadditional carrier represent quotients and multiplicands.

30. A combination as defined in claim 28, wherein said first indexingdevice comprises a dial disk rotatable in two directions and saidadditional carrier comprises a rotary digit wheel, said third indexingdevice comprising means for index ing said digit wheel by one incrementin response to rotation of said dial disk in either direction.

31. A combination as defined in claim 30, wherein said lastmentionedmeans comprises a stop movable from a neutral position and extendinginto the path of a finger during rotation of said dial disk, and alinkage coupling said stop with said digit wheel.

32. A combination as defined in claim 31, further comprising blockingmeans actuatable to disengage said linkage from said digit wheel.

1. In a calculating instrument, particularly for use by children, acombination, comprising carrier means comprising two carriers eachprovided with a sequence of symbols and each including a rotary digitwheel, said digit wheels being coaxial with each other and one thereofhaving indexing means for rotating the other thereof through a singleincrement in response to rotation of said one wheel through apredetermined number of increments, the symbols of said wheelsconstituting digits and each of said wheels having a single row ofcircumferentially extending digits including two groups of digits''''0'''' to ''''9''''; moving means for moving said carriers through adesired number of unit increments in each of which at least onedifferent symbol is located in a predetermined position to represent agiven numerical expression, said moving means including a finger flangeon each of said wheels; and yieldable detent means cooperating with saidfinger flanges to normally hold said means against rotation.
 2. In acalculating instrument, particularly for use by children, a combinationcomprising carrier means comprising a plurality of indexible wheelsincluding a first and a second wheel each provided with a sequence ofsymbols including a row of digits extending circumferentially of eachwheel; and moving means for moving said wheels through a desired numberof unit increments in each of which at least one different symbol islocated in a predetermined position to represent a given numericalvalue, said moving means comprising a first device for indexing saidfirst wheel through increments of predetermined magnitude and a seconddevice for indexing said second wheel through a single increment inresponse to indexing of said first wheel through a predetermined numberof increments, said second device comprising a stationary cam, followermeans movably mounted on said first wheel, and motion receiving meansprovided on said second wheel, said cam being arranged to move saidfollower means into torque transmitting engagement with said motionreceiving means in predetermined angular positions of said first wheel.3. In a calculating instrument, particularly for use by children, acombination comprising carrier means including at least one carrierprovided with a sequence of symbols and being movable between aplurality of positions in each of which at least one of said symbolsassumes a predetermined position to represent a given numericalexpression; moving means comprising a rotary dial disk for moving saidcarrier through a desired number of unit increments in each of which atleast one different symbol is located in said predetermined position; anumber wheel registering with said dial disk; and adjustable indicatingmeans for pinpointing a selected number on said wheel.
 4. In acalculating instrument, particularly for use by children, a combination,comprising carrier mEans including at least one carrier provided with asequence of symbols and being movable between a plurality of positionsin each of which at least one of said symbols assumes a predeterminedposition to represent a given numerical expression; moving means formoving said carrier through a desired number of unit increments in eachof which at least one different symbol is located in said predeterminedposition; said moving means comprising a dial disk which is rotatable intwo directions and has a group of finger holes; a support for said dialdisk; and a number wheel mounted on said support for movement betweentwo positions, said number wheel having a first set of numbers eachregistering with one of said finger holes in one position of said numberwheel and a second set of numbers each registering with one of saidfinger holes in the other position of said number wheel.
 5. Acombination as defined in claim 4, wherein said carrier comprises anindexible digit wheel.
 6. A combination as defined in claim 4, whereineach symbol of said carrier represents the same numerical value.
 7. Acombination as defined in claim 4, wherein the symbols of said carrierconstitute digits each representing a different numerical expression. 8.A combination as defined in claim 4, wherein the first of said carriershas symbols representing unit values and the second carrier has symbolsrepresenting multiple unit values.
 9. A combination as defined in claim8, wherein each symbol of said second carrier represents 10 unit values.10. A combination as defined in claim 4, wherein said first set ofnumbers includes a ring of numbers 1-10 running in a clockwise directionand said second set includes a ring of numbers 1-10 running in acounterclockwise direction, the numbers of said first set alternatingwith the numbers of said second set.
 11. A combination as defined inclaim 4, further comprising stop means adjacent to said dial disk toarrest the disk by extending into the path of movement of a finger whichis inserted into a selected finger hole to rotate said dial disk in oneof said directions.
 12. A combination as defined in claim 11, whereinsaid stop normally assumes a neutral position and is yieldable to fingerpressure to move through a predetermined distance to either side fromsaid neutral position.
 13. A combination as defined in claim 12, whereinthe numbers of said sets on said number wheel are equidistant from eachother and wherein the distance between successive numbers of either setcorresponds to the extent to which the stop is movable from said neutralposition.
 14. A combination as defined in claim 4, wherein said carriercomprises a rotary digit wheel and further comprising yieldable detentmeans for normally holding said wheel against rotation.
 15. Acombination as defined in claim 4, wherein said carrier means comprisestwo carriers each of which constitutes a rotary digit wheel having anannulus of symbols including two sets of digits ''''0'''' to ''''9''''.16. A combination as defined in claim 4, further comprising means forproducing audible signals in response to each incrementing of saidcarrier.
 17. In a calculating instrument, particularly for use bychildren, a combination comprising carrier means comprising two firstcarriers each constituting an indexible digit wheel and two secondcarriers constituting endless belts each driven by one of said wheels,each of said carriers being provided with a sequence of symbolsincluding a row of digits provided on and extending circumferentially ofeach of said wheels and at least one row of symbols on each of saidbelts, one row of symbols including unit symbols and the other rowincluding decade symbols; and moving means for moving said carriersthrough a desired number of unit increments in each of which at leastone different symbol is located in a predetermined position to representa give numerical value, said moving means including means for indexingone of said wheels through increments of predetermined magnitude andmeans for indexing the other wheel through one increment in response toindexing of said one wheel through 10 increments.
 18. A combination asdefined in claim 17, further comprising a pair of pulleys, each of saidbelts being trained over one of said pulleys and the respective digitwheel.
 19. A combination as defined in claim 18, wherein each of saidbelts is provided with a line of perforations and each of said digitwheels comprises a sprocket whose teeth engage the respectiveperforations.
 20. A combination as defined in claim 17, furthercomprising a wall overlying said digit wheels and having a pair ofwindows each of which permits observation of a single digit on one ofsaid digit wheels.
 21. A combination as defined in claim 17, wherein oneof said belts is provided with two rows of unit symbols and wherein onerow of said unit symbols is offset with reference to the other row ofunit symbols.
 22. A combination as defined in claim 21, furthercomprising masking means movable between first and second positions inwhich it respectively conceals the one and the other row of said unitsymbols, and means for moving said masking means between said positionsin response to indexing of the corresponding digit wheel through saidpredetermined number of increments.
 23. A combination as defined inclaim 22, wherein the means for moving said masking means comprises cammeans provided on said last-mentioned digit wheel and shifting meanscoupled to said masking means and having follower means arranged totrack said cam means.
 24. A combination as defined in claim 17, furthercomprising a wall overlying said carriers and having a pair of apertureseach permitting observation of a limited number of symbols on one ofsaid belts and a pair of windows each permitting observation of a singledigit on one of said wheels.
 25. A combination as defined in claim 24,further comprising shutter means movable to and from a predeterminedposition in which it conceals the digits behind said windows.
 26. Acombination as defined in claim 25, further comprising record receivingmeans to permit recordal of mentally performed calculations and shieldmeans operatively connected with said shutter means to overlie saidrecord receiving means in response to movement of the shutter means awayfrom said predetermined position.
 27. A combination as defined in claim26, wherein said shield means consists at least in part of lighttransmitting material.
 28. In a calculating instrument, particularly foruse by children, a combination comprising carrier means comprising apair of first indexible carriers each provided with a sequence ofsymbols which include digits, said carriers being movable between aplurality of positions in each of which at least one of said symbolsassumes a predetermined position to represent a given numericalexpression; a first indexing device actuable to index one of said firstcarriers through increments of unit length; a second indexing device forindexing the other first carrier by a single increment in response toindexing of said one first carrier through a predetermined number ofincrements; an additional indexible carrier having digits representing aseries of numerical values; and a third indexing device operative toindex said additional carrier in response to each actuation of saidfirst indexing device.
 29. A combination as defined in claim 28, whereinthe digits of said additional carrier represent quotients andmultiplicands.
 30. A combination as defined in claim 28, wherein saidfirst indexing device comprises a dial disk rotatable in two directionsand said additional carrier comprises a rotary digit wheel, said thirdindexing device comprising means for indexing said digit wheel by oneincrement in response to rotation of said dial disk in either direction.31. A combination as defined in claim 30, wherein said last-mentionedmeans comprises a stop movable from a neutral position and extendinginto the path of a finger during rotation of said dial disk, and alinkage coupling said stop with said digit wheel.
 32. A combination asdefined in claim 31, further comprising blocking means actuatable todisengage said linkage from said digit wheel.